On September 10, Larry Tesler got in line around 7 a.m. at the Apple Store on University Avenue in Palo Alto, Calif., to wait along with a clutch of Apple fans who wanted to be among the first to get a new iPhone. An hour and 45 minutes later, the former chief scientist at Apple walked out with a space-gray iPhone 5S and a soft case.

Tesler left Apple 16 years ago, but he still keeps close watch on how the company is evolving its products, especially the user interface. He pioneered the concept of "cut-copy-paste" during his time at Xerox PARC in the 1970s. In the following two decades -- Tesler spent 17 years at Apple -- he was deeply involved in the user interface design of the Lisa, Macintosh, and Newton, a precursor to the iPhone. Following his time at Apple, Tesler served as vice president of the shopping experience at Amazon and later, as head of user experience design and research at Yahoo.

So when Tesler speaks, his words reflect the weight of authority. After a few weeks of using Apple's latest phone, how does this veteran of myriad user interface battles rate iOS 7?

"It's beautiful and I like it, but there are a lot of little bugs that are annoying and a few interface changes they made that need to be refined," he said.

iOS 7 screenshot

"Organizing all your icons is a lot of push, pull, watch things flicker, drag, let go at just the right place. If you accidentally let go, then it might go into the wrong folder or go onto the next page, or something else might go to the next page. There was already a little of that before, but they made it worse," Tesler said. "Also, if you do certain things, iOS 7 decides that you must have made a mistake and you are not happy with it. So it will undo everything you did since you first went into this 'wiggle' mode. It needs a little more tweaking."

Tesler also thought novice users might find the presentation of a blank page disconcerting. "If you go to a new page, which it sometimes does for you automatically, the new page is blank. For beginners, suddenly seeing a blank window come up will make them think they lost everything," he said.

He also liked the flatter layout as well as the move away from skeuomorphism, with wood veneers and brushed chrome.

"I didn't think I would like it at first, but I actually do like it quite a lot. However, many things have very thin lines. I don't think they tested it on anyone over 50 years old," he said.

Tesler also noted that some applications, including from Apple, are a bit rough in spots. "Sometimes you see a word which is a command you can tap. There is probably a very thin outline around it, but it's too faint for me to see, and a lot of people won't notice it. And next to it there is some text the same color or a different color or a slightly different baseline. But there are cases where it looks like the two are related. You read them all as a single thing, and you misunderstand what you are seeing. It's just buggy right now, and some of that is just waiting for new applications to release."